In the field of biology, a technique for efficiently separating one type or class of cell from a complex cell suspension would have wide applications. For example, the ability to remove certain cells from a clinical blood sample that were indicative of a particular disease state could be useful as a diagnostic for that disease.
It has been shown, with limited success, that cells tagged with micron sized (0.1 xcexcm) magnetic or magnetized particles can be removed or separated from mixtures using magnetic devices that either repel or attract the tagged cells. For the removal of desired cells, i.e., cells which provide valuable information, the desired cell population is magnetized and removed from the complex liquid mixture (positive separation). In an alternative method, the undesirable cells, i.e., cells that may prevent or alter the results of a particular procedure, are magnetized and subsequently removed with a magnetic device (negative separation).
Several magnetic devices exist that can separate micron sized ( greater than 0.1 xcexcm) magnetic particles from suspension. Particles of this size do not form a stable colloid and will settle out of the suspension. Smaller, colloidal particles ( less than 0.1 xcexcm) have a larger surface to volume ratio, are subject to random thermal (Brownian) motion, and are present in much greater numbers per unit mass. These properties make it more likely that colloidal particles will find a rare cell population among a much larger population of non-desired cells to allow positive selection. It is also likely that a greater percentage of the a particular population of cells could be labeled and subsequently depleted by these numerous, mobile particles to allow negative selection.
However, smaller magnetic particles present unique problems. The magnetic force of attraction between these smaller particles and the separating magnet is directly related to the size (volume and surface area) of the particle. Small magnetic particles are weak magnets. The magnetic gradient of the separating magnetic device must increase to provide sufficient force to pull the labeled cells toward the device.
A need exists for the development of a magnetic device capable of efficiently separating small magnetic particles from a liquid.
The magnetic pole device of the present invention has four polar magnets and any number of interpolar magnets adjacent to and in between said polar magnets. The interpolar magnets are positioned to progressively rotate towards the orientation of the four polar magnets. Such a magnetic device creates a high flux density gradient within the liquid sample and causes radial movement of magnetized particles toward the inner wall of the surrounding magnets.
In another aspect, the present invention relates to a method of separating non-magnetized cells from magnetized cells using the magnetic device of the present invention.